Using Rhino 8 in Windows, dark interface mode, the menu bar switches to light mode when Main window title bar is unchecked.
Furthermore, after clicking outside the Rhino window and the expected text fading to grey, if I click back inside in the active viewport, the text remains grey. Only clicking inside a different viewport turns the text back to black.
Thanks for reporting it!
RH-89950 v8 dark mode shows light mode menu bar